With the exception of boasting an impressive cast for what is essentially a schlocky sci-fi movie (Is “schlock-fi” a thing? I’m making it a thing.), not much about Life grabs you. In fact, it’s arguable that the most interesting buzz surrounding it has been the silly rumors and fan theories insisting it might actually be a stealth prequel to the recently announced Venom film. It should come as no surprise that this isn’t remotely true, but the good news is that Life doesn’t need to resort to such desperation. This is a perfectly serviceable exercise in claustrophobic, monster movie space horror—its premise is essentially Alien by way of Gravity, with all the blockbuster gloss that entails. However, even all that big studio luster can barely hide the cheap thrills underpinning Life, a film that is essentially about a tentacle monster ripping through human flesh for about 100 minutes. I can think of worse ways to spend a Friday evening.

What’s more, neither director Daniel Espinosa nor screenwriters Rhett Reese and Paul Wernick seem to concerned about gussying up the formula. There’s a great economy to the setup, which finds the crew of the International Space Station recovering a probe from Mars. The difficulty of the task—an astronaut (Ryan Reynolds) has to disembark from the station and literally grab the probe as it passes through—lends itself to a swell of emotion as John Ekstrand’s triumphant score blares over the title screen. Within the space of a few minutes, you realize the enormity of a dream that will swiftly become a nightmare, as that sweeping score has some sinister notes rumbling beneath, hinting at the doom that obviously awaits.

Because let’s face it: you’ve seen Alien. I’ve seen Alien. Most of us even saw Prometheus. This never ends well, especially when it involves the space crew discovering an organism. At first, the creature here—which is later dubbed “Calvin”—is an innocuous single-cell organism that’s only capable of being poked and prodded by the resident biologist (Ariyon Bakare). Eventually, though, it grows at an alarming rate before numerous screw-ups allow it to escape its test tube and terrorize the rest of the crew. All of this happens within the first third of the film, meaning Life isn’t exactly shy about its intentions to tear flesh and spill blood.

As the umpteenth riff on Alien, Life obviously has a lot of familiarity to outrun, and Espinosa senses that the way out is through. Rather than subvert the formula, Life has some wry fun with it: a surprising early death signals that, at the very least, it’s not fucking around, and most of the death sequences that follow are harrowing as hell. One finds a crewmember desperately attempting to repair some external damage, only to confront Calvin in a scene that eventually echoes the panic attack inducing qualities of Gravity. It’s genuinely unsettling to watch because Espinosa doesn’t flinch: we look on in horror as this doomed crew member dies in what might be the most agonizing fashion imaginable, and the camera lingers as every unnerving moment unfolds on the actor’s face: the frenzied terror, the sudden realization of their grim fate, the bleak resignation.

It’s moments like this especially that Life proves its commitment to being a pure, unfiltered horror movie. Aside from the obligatory quiet beats to allow the characters (and the audience) to catch their breath, the film is a relentless parade of suspenseful sequences, some of which are punctuated with gory exclamation points. Espinosa exploits the setting for its maximum, disorienting potential: his swirling camerawork tilts the frame about, simulating the nauseating uneasiness of a zero-gravity environment. Calvin’s stealthy approach—it ends up hiding in shafts and air vents, not unlike another very famous xenomorph—is made all the more uneasy by this lack of stability.

Given the setting, it’s perhaps an expected tactic, but it adds a new dimension to the unpleasantness on display here. Life is at its best when Espinosa embraces the primal horror of the situation and effectively crams the audience in right alongside the characters, effectively subjecting them to the same claustrophobic terrors as the crew. There’s a genuinely gritty, weighty texture to it all, too; sure, the film relies on digital effects (Calvin himself being the most obvious example), but they’re integrated rather seamlessly. Forgive the obvious wordplay, but Life has an actual gravity that registers. Every decision the crew makes feels important, leading to a natural tension, particularly when they involve moving from one compartment in the station to the other. Calvin could strike at any time, and the suspense is palpable—especially since he grows into something more horrific each time he reappears.

In theory, the cast of familiar faces also adds some gravity. It’s an obvious enough shorthand to cast amiable, well-known actors to compensate for some thinly-sketched characters, but it mostly works here. Ryan Reynold expectedly yuks it up as the onboard jokester, Jake Gyllenhaal is a brooding war veteran who’d rather hang out alone on space than deal with earthbound problems, and Rebecca Ferguson is the no-nonsense quarantine officer tasked with making difficult, divisive decisions. They’re all fine, if not broadly written to engender maximum pathos with minimum effort. I mean, just about the only thing we know about Hiroyuki Sanada’s pilot character is that his wife gives birth his daughter early on the film, which is just about the easiest way to generate sympathy. It works well enough, and an international crew cooperating in the face of insurmountable odds almost makes it feel like the yin to The Martian’s yang—it’s almost like if that film had gone straight to hell.

By the end, though, Life has dispensed with any and every pretense of being a character study anyway. Even though its climax hinges on unfathomable decisions and heroic sacrifices, it feels deviously wry as the film really hits its stride and admits its characters are pretty expendable. The final ten minutes or so thrive on indelible images and Ekstrand’s now firmly unsettling score—it’s by far the best stretch of the film, and it does leave you wishing the rest of Life was operating on this level. Even though I had the final reveal pegged, it was nonetheless cool to watch such a ballsy ending unfold in an otherwise rote blockbuster.

Don’t get me wrong: Life is a fine riff on this (very) familiar theme, but had it embraced the bleak, Twilight Zone style verve of its finale, it’d feel more substantial. As it stands, it’s a solid if not perfunctory effort that will only feel more redundant upon the release of Alien: Covenant—not that it’s this film’s fault that Ridley Scott is apparently committed to making Alien movies until the heat death of the universe, mind you.